In a printer capable of forming an image on an adverse side and a back side of a sheet, a reverse-running mechanism is provided for reversing a conveying direction of a sheet already formed with an image on its adverse side and then directing the sheet to an inlet side of an image forming unit to form an image on a back side of the sheet.
In such a conventional printer, a first sheet passage extends from an outlet side of the image forming unit to the reverse-running mechanism, and a second sheet passage extends from the reverse-running mechanism to the inlet side of the image forming unit. A pivotally movable changeover flap is provided at a bifurcate portion between the first and second sheet passages for selectively shutting off the one of the first and second sheet passages.
An opening portion is formed in a frame for partly opening the second sheet passage in order to remove a sheet jammed at the second sheet passage. A cover is pivotally movably provided to the frame for opening and closing the opening portion. The changeover flap is provided at the cover, and the second sheet passage is defined between an inner surface of the cover and the changeover flap. (0007B front half) Further, sheet sensors are provided to detect a sheet passing through the first and second sheet passages.